public Void visit(FunctionDeclaration funcDeclar, Void params) {
        super.visit(funcDeclar, params);
        if (!symbolTable.insert(funcDeclar)) {
            ErrorHandler.getInstance()
                    .addError(new ErrorType("Function '" + funcDeclar.getName() + "' has already been defined"));
        } else {
            symbolTable.set();

            for (VarDeclaration varDeclar : ((FunctionType) funcDeclar.getType()).getParams()) {
                this.visit(varDeclar, params);
            }

            for (Statement st : funcDeclar.getBody()) {
                if (st instanceof VarDeclaration) {
                    this.visit((VarDeclaration) st, params);
                }

                if(st instanceof Invocation) {
                    this.visit(((Invocation) st).getName(), params);
                }
            }

            symbolTable.reset();
        }
        return null;
    }